Brake system control method and system

Abstract

A method for controlling a brake system of a vehicle includes the steps of predetermining (502) a clamping force threshold detectable by a caliper sensor, identifying (508) a defined caliper stiffness model, estimating (510) an estimated clamping force value (FS) using the caliper stiffness model, and generating (512) an actuator control signal (SC) based on the estimated clamping force value (FS).

Description

[Technical field]

[0001] The present invention relates to a vehicle braking system, and more particularly to a control method and relative system for a vehicle braking system. [Background technology]

[0002] In modern vehicles, e.g. passenger cars, braking systems equipped with electronic BBW technology (from the acronym "brake by wire") braking systems are becoming increasingly common.

[0003] In a BBW technology electronic brake system, it is essential to know the force exerted by a pair of brake caliper pads on each brake disc during the braking phase, so that the force can be adjusted by the BBW electronic brake system with a typical closed loop control system. The value of the force exerted by the caliper is compared with a reference force value required for braking by the vehicle driver or electronic driver assistance system in order to accurately ensure that the braking force reaches said required reference force value.

[0004] Such comparisons are performed not only in the typical case of a braking request, but also in specific cases where the BBW electronic braking system must respond to requests from additional electronic systems that the vehicle may be equipped with, such as a wheel antilock braking system (ABS) or an electronic stability control system (ESC), or to low adhesion conditions on the vehicle itself.

[0005] In the prior art, there are two options for obtaining feedback regarding the level of applied clamping force:

[0006] 1. Use of a force sensor (which can be a pressure sensor or a torque sensor) that covers the full range of motion of the caliper.

[0007] 2. Use of an estimator that indirectly calculates the applied force based on additional measurements (position, current, temperature, etc.) obtained from the calipers of the BBW system.

[0008] Option 1 has several limitations in terms of feasibility, cost, resolution / precision, and reusability.

[0009] With regard to feasibility, in some cases it is not possible to provide a sensor that can read the entire range of motion of the brake caliper in the small space available on the caliper itself.

[0010] In terms of cost, developing and validating sensors with extended read ranges can be very expensive.

[0011] Increasing the sensor's reading range can result in reduced accuracy and resolution.

[0012] Regarding reusability, unless sensors with a very wide range are used, even for actuators requiring a low reading range, a sensor with an appropriate range must be selected for each application and the same sensor cannot be used for multiple applications with different ranges, e.g. different vehicle ranges.

[0013] Option 2 has the problem of many uncertainties and variations in part life due to, for example, efficiency variations, pad wear, actuator and caliper manufacturing parameter variations, thermal effects, friction force variations, etc. These issues can lead to poor estimates, especially in the initial part of the low force braking event, and the need to determine and detect the pad-disc contact point with high accuracy.

[0014] The object of the present invention is to propose a method and a system for controlling a braking system, making it possible to at least partially overcome the limitations and drawbacks of the prior art solutions. Summary of the Invention [Means for solving the problem]

[0015] This object is achieved by a method for controlling a braking system according to claim 1 and by a control system according to claim 13.

[0016] Some advantageous embodiments are the subject matter of the dependent claims. [Brief description of the drawings]

[0017] Further characteristics and advantages of the method and related system according to the invention emerge from the following description of preferred embodiments thereof, given purely as non-limiting examples with reference to the attached figures, in which:

[0018] [Figure 1] FIG. 1 shows, by means of a block diagram, an electronic control system for a braking system of a vehicle according to an embodiment of the invention.

[0019] [Diagram 2] FIG. 2 shows by means of a block diagram an electronic control system for a braking system of a vehicle according to a further embodiment of the invention.

[0020] [Diagram 3] FIG. 3 is a stiffness curve graph comparing partly measured and partly estimated forces and movements obtained according to an embodiment of a control method according to the present invention.

[0021] [Figure 4] Figures 4 and 4a are two stiffness curve graphs comparing force vs. travel and force vs. time, respectively, including the hysteresis characteristics of the caliper. [Figure 4a] Figures 4 and 4a are two stiffness curve graphs comparing force vs. travel and force vs. time, respectively, including the hysteresis characteristics of the caliper.

[0022] [Diagram 5]FIG. 5 is another stiffness curve graph comparing force versus travel with hysteresis, illustrating the transition between the rising and falling curves of the clamping force.

[0023] [Figure 6] FIG. 6 is a flow chart of a method for controlling a braking system of a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the accompanying drawings, reference numeral 1;100 is used to generally indicate diagrammatically an electronic control system for a braking system according to some embodiments of the present invention. In particular, the control system is applied to a brake-by-wire braking system in a distributed architecture, where each corner of the vehicle is independently controlled in a closed-loop mode to minimize the error between the value of the target braking force, i.e. the reference (FR) braking force, and the strength of the braking force actually applied by the brake calipers.

[0025] It should be noted that the values ​​related to the braking target and the magnitude of the force applied by the caliper may depend on the control method employed, the sensors used, or the topology of the corner, and may be, for example, but not limited to, force, pressure, or torque. These measurements are interrelated and can be easily converted between each other. Therefore, in the following description, such interrelated quantities will be generally referred to as "force" or "clamping force."

[0026] Additionally, elements common to the various embodiments are designated with the same reference numerals.

[0027] In this specification, although not shown in the figures, the term "vehicle" refers to any vehicle or automobile, also of a commercial type, having two, three, four or more wheels.

[0028] Additionally, the term "brake system" refers to the collection of all components (from mechanical and / or electrical or electronic components to brake fluid) that contribute to application of the vehicle's service brakes or application of the vehicle's parking brakes, also not shown.

[0029] 1 and 2 are block diagrams of possible embodiments of the system 1. In FIG.

[0030] In some embodiments, the control system comprises a vehicle control module 101 .

[0031] The vehicle control module 101 is, for example, a hardware module and / or software logic within a main hardware module, and is configured, among its intended tasks, to receive a braking request RF (deceleration request).

[0032] This braking request RF may come from a brake pedal (not shown) operable by the vehicle driver and processed, for example, by EBD logic (Electronic Brake-force Distribution, not shown) implementable by the vehicle control module 101, or may come from automated vehicle driver assistance logic, for example AEB logic (Autonomous Emergency Brake, also not shown).

[0033] The vehicle control module 101 may be configured to determine the reference force value FR based on the braking request RF and possibly other information obtained from sensors associated with the braking system, or the vehicle in general.

[0034] In another embodiment, the vehicle control module 101 is external to the control system 1;100 that is the subject of the present invention and provides the control system 1;100 with a value of the reference force FR.

[0035] The system 1;100 further comprises one or more corner detection devices 10 operatively associated with the corners of the vehicle.

[0036] These corner detection devices 10 are configured to detect corner information representative of the braking system at a corner of the vehicle. As used herein, the phrase "corner information representative of the braking system at a corner of the vehicle" actually refers to information related to each braking system, even if they are not necessarily physically located at opposite corners.

[0037] The corner detection device 10 comprises an actuator sensor 102 suitable for obtaining information relating to the state of a caliper actuator, for example an electromechanical or electrohydraulic actuator operable to command the clamping and release of a respective brake caliper.

[0038] More specifically, in some embodiments, the actuator sensors 102 comprise position sensors, electrical voltage sensors, current sensors, temperature sensors, and the like.

[0039] In such a case, the information obtained by the actuator sensor 102 is, for example, as follows:

[0040] Position of the electromechanical or electrohydraulic actuator of the brake caliper.

[0041] A quantity derived from the position of an electromechanical actuator of a brake caliper, such as velocity, acceleration, or derivative of acceleration (snatch or jerk).

[0042] Supply voltage / PWM (Pulse Width Modulation) of electric motors suitable for driving electromechanical or electrohydraulic actuators, and further derived quantities (e.g. peak, filtered average value of electrical voltage, power derived from current, etc.).

[0043] The current absorbed by the electric motor and further derived quantities (e.g. current peak, filtered average value, power derived from the electric voltage, estimated consumption, efficiency, absorbed power, etc.).

[0044] The external temperature of the electromechanical or electrohydraulic actuator and / or electric motor.

[0045] The corner detection device 10 further comprises, for each corner, a force sensor 104 suitable for obtaining information regarding the clamping force applied to the brake disc by the brake caliper.

[0046] In one embodiment, the force sensor 104 is suitable for measuring the clamping force exerted by the brake caliper at least within a range limited to an initial part of the operating range of the brake caliper, i.e. an initial part of the piston stroke for an electromechanical actuator, or an initial part of the pump float stroke or caliper piston stroke in the case of an electrohydraulic actuator.

[0047] In other words, the force sensor 104 can have a force reading range that is lower than the operating range of the brake caliper.

[0048] In other embodiments, the force sensor 104 functions or is used to function as a binary sensor, i.e., a force switch, suitable only for detecting whether the clamping force exerted by the caliper exceeds a predetermined threshold. In this case, for example, the corner information consists of information (e.g., a "flag") representative of the start of a force phase by the electromechanical actuator, i.e., the start of a load phase when the piston of the electromechanical or electrohydraulic actuator starts exerting force and passes from an unloaded position to a position where it starts to load the brake caliper.

[0049] The system 1 further comprises a force estimation module 110 configured to determine an estimated force value FS based on a clamp stiffness model represented by a theoretical stiffness curve Fx relating the clamping force applied by the actuator to the position P of the piston of the electromechanical or electrohydraulic actuator.

[0050] The caliper stiffness model is provided in stiffness modeling module 120 .

[0051] 1, the system employs a force sensor 104 configured to measure clamping forces at least within a lower bounded range of the caliper operating range, and the stiffness modeling module 120 constructs a theoretical stiffness curve Fx based on information obtained from the force sensor and information about the state of the caliper actuator. The following description describes several examples of model building algorithms.

[0052] In this embodiment, the force estimation module 110 is configured to estimate the theoretical stiffness curve within a clamping force range that is beyond the sensor reading range, within the clamping force range up to a maximum clamping force value of the caliper, or in any case beyond some predefined clamping force threshold within the sensor reading range, e.g. below a value where the measurement accuracy of the sensor is considered satisfactory and above a value where the measurement accuracy of the sensor is considered unsatisfactory.

[0053] In some embodiments, the electronic control system is configured to use the clamping force information coming from the force sensor when the reference force value FR is below a threshold established for the force sensor, and to use the estimated force value FS when the reference force value FR is above the threshold.

[0054] In other words, the stiffness model is used to estimate forces beyond the sensor reading range to provide closed-loop control feedback over the entire motion range of the corner.

[0055] For example, the comparison between the reference force value FR and a threshold value may be performed by the force estimation module 110 based on information coming from the actuator sensor 102, for example the position of an electromechanical actuator piston.

[0056] The system 1 ; 100 also includes a brake control module 130 .

[0057] The brake control module 130 is a hardware module and / or software logic, for example in the main hardware module, configured to receive a signal representative of the estimated force value FS coming from the estimator module and a signal representative of the actual force FA detected by the force sensor. The brake control module 130 is configured to compare one of these two signals with a reference force value FR (e.g., by whether the reference force value FR is below or above a predefined threshold) and to generate, based on the comparison, a control signal SC for an electromechanical or electrohydraulic actuator of a brake caliper of the brake system (this actuator is represented diagrammatically outside the system 1; 100 and is denoted by the reference AE).

[0058] It should be noted that the control signal SC is for example a reference value (set point) of the current or electrical voltage (PWM) supplied to the electromechanical actuator AE of the brake caliper.

[0059] In one embodiment, the system 1 also comprises an electronic drive module DR for the electromechanical actuator AE.

[0060] The brake control module 130 may be configured to provide a control signal SC to the electromechanical actuator AE by means of an electronic drive module DR.

[0061] The drive module DR is configured to receive a control signal SC and thus a brake demand level (percentage / PWM) and consequently generates a drive signal SC' that is supplied to the electromechanical actuator AE, e.g. an electric drive current that is supplied to an electric motor suitable for moving the electromechanical actuator AE.

[0062] In one embodiment, the stiffness modeling module 120 is configured to model the theoretical stiffness curve as a parabolic curve, a cubic curve, or an exponential curve based on the characteristics of the caliper within the reading range of the force sensor.

[0063] More specifically, in some embodiments, the stiffness modeling module 120 is configured to model the theoretical stiffness curve in one of two forms depending on the characteristics of the caliper (e.g., based on shape, friction, etc.):

[0064] For example, if during the "offline" system development and testing phase it is found that a specified model, e.g. a parabolic, cubic or exponential curve, correctly represents the entire operating range of the caliper, the specified model can be built based on information obtained from the sensor within its reading range and the same curve can be used to estimate forces at the top of the caliper's operating range, i.e. above the reading range of the sensor or in any case above a preset threshold.

[0065] On the other hand, if it turns out that the identified model, e.g., a parabolic, cubic or exponential curve, correctly represents only the lower side of the operating range of the caliper for which the sensor readings are used, the identified model is used to use the sensor readings. A linear extrapolation is then performed using the identified model to extend the model at the upper part of the operating range of the caliper, outside the area covered by the sensor, where the caliper stiffness may be better identified as a linear curve instead of a parabolic, cubic or exponential curve.

[0066] In other words, as can be seen from Figure 3, if the model is fitted only to the lower part of the operating range, in this lower part the curve has a non-linear characteristic, for example a parabolic or cubic characteristic, while the upper part (represented by the dashed line) is extrapolated from the model starting from the slope of the final section of the lower part, and the extrapolation has a linear characteristic.

[0067] The stiffness modeling module 120 can be configured to perform the model identification routine according to a variety of strategies.

[0068] The first is to use new information coming from the force sensors to identify the model in real time with every new brake system control cycle.

[0069] According to a second variant, model identification is performed only when predefined intermediate force thresholds are reached during the braking event (i.e. when the sensor threshold is dropped). The intermediate force thresholds may be selected at regular intervals (e.g. every 1000 N) or may be distributed by increasing the number of samples in the region of maximum non-linearity and decreasing the number of samples where the curve is more linear or nearly linear.

[0070] According to a third form, model identification is performed once per braking event after collecting all data from the force sensors, for example when the actuator is not braking.

[0071] In some embodiments, the caliper stiffness modeling module may be configured to add obsolete parameters related to the data used during the model fitting step. Indeed, there may be more data available at the bottom of the caliper's operating range, where the majority of braking events occur, and less data at higher levels of force. Thus, data related to higher levels of force may be old data related to braking events that occurred much earlier than the braking event that the system is controlling.

[0072] Thus, during the modeling step, the fitting algorithm can introduce an obsolescence parameter related to the available data, so that the most recent data has a greater weight than older data, allowing the model estimation process to use the available information on the full operating range of the sensor, but to be more sensitive to stiffness changes due to, for example, pad wear or thermal effects on the disc and caliper.

[0073] It should be noted that the choice of how often to run the model identification routine may result from a trade-off between the need to update the model frequently and optimizing the computational load.

[0074] 2, employing a binary force sensor 104 configured or used solely to provide information regarding reaching a predefined clamping force threshold, the stiffness model 120 is obtained during the electronic control system configuration step, i.e., in an "offline" mode. For example, in this case, measurements of the caliper actuator piston position and the caliper clamping force are performed by external sensors during a force ramp, and the collected data is used to determine the parameters of the stiffness model.

[0075] The binary force sensor 104, in other words, senses the presence or absence of a clamping force. The sensed force may be the contact force of the pad and the disk. The sensor detects the presence of a force, for example, when the force exceeds a certain predefined threshold. When this threshold is exceeded, the estimation module applies a model provided by a stiffness modeling module 120 (represented external to the control system in FIG. 2) to obtain an estimated force value FS as a function of the information received from the actuator sensor 102.

[0076] In this case, the control system 100 may configure a storage module 122 in which the stiffness models obtained “off-line” from the stiffness modeling module 120 are stored. The storage module 122 is accessible by the force estimation module 110.

[0077] The stiffness modeling module is configured to take into account hysteresis effects present in the caliper so that the curve of increasing clamping force does not match the curve of decreasing force as the required force decreases.

[0078] More specifically, in one embodiment, the stiffness modeling module is configured to implement this hysteresis effect by identifying a stiffness model only for the force increasing phase and deriving the decreasing phase of the curve by translating the model by a predefined amount.

[0079] The stiffness curve Fx as a function of piston position including the caliper hysteresis effect is shown in FIG. 4. The clamping force reduction phase is noted, which is substantially the same as the change in the increase phase. FIG. 4a shows the same stiffness curve as a function of time. In a variant of the embodiment, information from the force sensor is used to distinguish two models for both the apply and release phases of the braking event.

[0080] In either case, once the two curves are obtained, the modeling module is configured to implement a mechanism that connects the two curves when a specific force modulation is required and the actuator changes direction from a force increasing phase to a force decreasing phase or vice versa.

[0081] In particular, as shown in FIG. 5, the modeling algorithm implements several additional transition curves that can be identified and modeled as linear behavior, parabolic curves, cubic curves, exponential curves, or filters based on the actual behavior of the caliper.

[0082] To properly implement this mechanism, the modeling module may receive information regarding the direction of movement of the actuator (during application or release) from a sensor that detects the position of the piston of the electromechanical or electrohydraulic actuator AE (or other relevant information).

[0083] In some embodiments, the force sensor 104 is mechanically integrated into an electromechanical or electrohydraulic actuator, although such integration may be performed according to alternative embodiments.

[0084] For example, in one embodiment, the force sensor is constantly subjected to an applied force that exceeds the clamping force threshold. In this embodiment, the sensor must be mechanically designed to withstand the full range of caliper forces without permanent deformation or damage. In terms of the force being measured, it can be designed to only measure up to the threshold where the full scale of the interface is reached (a solution that provides maximum resolution). Alternatively, the sensor can have a wider interface scale but provide less accurate measurements above the threshold.

[0085] In one embodiment, the sensor is integrated with a mechanical design that only stresses the sensitive part of the sensor up to a threshold clamping force. This solution allows the sensitive part of the sensor to be designed to withstand only one force up to the threshold, without requiring a mechanical structure that can withstand the full force range of the caliper.

[0086] Referring now to the block diagram of FIG. 6, a method 500 for controlling a vehicle braking system in accordance with the present invention will now be described.

[0087] The method 500 includes a symbolic start step STR.

[0088] The method includes predetermining (502) a clamping force threshold FT detectable by a caliper sensor, such threshold FT being lower than a maximum clamping force value achievable by the caliper.

[0089] As mentioned above, the clamping force threshold FT may be the maximum value of the sensor reading range or may be a threshold selected as a function of the accuracy of the caliper sensor.

[0090] The method 500 includes receiving (506) a value of a reference force (FR).

[0091] In some embodiments, the value of the reference force (FR) is received (504) by the vehicle control module 101, which generates (502) the value of the reference force (FR) based on the braking request (RF).

[0092] The method includes identifying (508) a caliper stiffness model, defined by a theoretical stiffness curve relating the clamping force applied by the caliper to the position of the caliper actuator, using a caliper stiffness modeling module.

[0093] If the value of the reference force FR is higher than the threshold FT, the method includes estimating (510) by the force estimation module 120 an estimated clamping force value FS using the caliper stiffness model and information correlating to the position of the electromechanical actuator.

[0094] The method also includes generating, by the brake control module 130, actuator control signals based on the estimated clamping force value FS and the reference force value FR (512).

[0095] In one embodiment, in which the caliper sensor has a reading range of at least from zero to a threshold value FT, if the value of the reference force FR is lower than the threshold value FT, the method includes generating (512'), by the brake control module, an actuator control signal SC based on the actual clamping force value FA measured by the caliper sensor.

[0096] In one embodiment, where the caliper sensor has a reading range of at least zero to a threshold value, determining 508 is performed based on clamping force information detected by the caliper sensor as a function of the caliper actuator status information.

[0097] In one embodiment, the step of identifying 508 comprises generating a theoretical stiffness curve of parabolic, cubic or exponential type over the entire operating range of the caliper.

[0098] In one embodiment variant, the step of identifying 508 consists of generating a theoretical stiffness curve having a first section of parabolic, cubic or exponential type in the force range up to the threshold value and a second linear section above the threshold value obtained by linear extrapolation starting from the slope of the final part of the first curve section.

[0099] In one embodiment of the method, the step of determining 508 is performed in real time with each new cycle of acquiring the information provided by the caliper sensor.

[0100] In one embodiment variation of the method, the step of identifying 508 is performed at the end of the braking event using a plurality of pieces of information provided by the caliper sensors during the braking event.

[0101] In a further embodiment variant of the method, the identification step 508 is performed during a braking event each time a predefined force sub-threshold is exceeded within the force range up to the threshold.

[0102] In one embodiment of the method, identifying 508 includes assigning a greater weight by the force estimator module to the most recent clamping force information provided by the caliper sensor.

[0103] In one embodiment variation of the method, a binary caliper sensor is used that is adapted to provide clamping force presence information when the clamping force reaches a predetermined threshold.

[0104] In one embodiment of the method, identifying step 508 further comprises estimating caliper hysteresis effects, said estimating comprising a predetermined amount of translation of a theoretical stiffness curve representing a phase of force application.

[0105] In one embodiment variant, the step of estimating the hysteresis effect is based on the detection of the clamping force of the caliper by a caliper sensor during the braking event release phase.

[0106] In the following, some advantages of the above-described control method and associated system are highlighted.

[0107] The use of a limited read range sensor in combination with a force estimation algorithm to extend measurements over the entire working range of the caliper has several advantages over prior art solutions that use higher range sensors or only use force estimates.

[0108] Compared to the option of using only a force estimation algorithm, the use of force sensors also allows for precise detection of contact points and correctly identifies variances in parameters and stiffness due to thermal effects, wear and aging of parts.

[0109] Additionally, the pad wear estimation of electromechanical calipers is more accurate and corner control at low levels of force has greater precision, thereby providing a better experience for the driver.

[0110] Using a limited range sensor compared to using a maximum read range sensor allows optimizing accuracy and resolution where it matters most: at low levels of force. Additionally, a limited read range sensor can be designed to withstand the forces involved, thus reducing packaging more suited to BBW system actuators, optimizing manufacturing costs.

[0111] Finally, the proposed solution allows the adoption of an easily scalable force sensor for various applications with different force ranges: the same physical sensor always measures and experiences the same clamping force threshold, but only the algorithm that estimates the above-threshold force may need customization to scale and accommodate the full operating range.

[0112] For the embodiments of the method and system for controlling a braking system according to the invention, those skilled in the art can modify, adapt and replace elements with functionally equivalents to meet their foreseeable needs without departing from the scope of the following claims. Each feature described as belonging to a possible embodiment can be obtained independently from the other described embodiments.

Claims

1. 1. A method of controlling a braking system of a vehicle, comprising: the braking system comprising at least one brake caliper, a caliper actuator operable to cause clamping / release of the brake caliper, and a caliper sensor adapted to detect a magnitude associated with clamping of the caliper; The method comprises: a step (502) of predetermining a clamping force threshold detectable by the caliper sensor, the clamping force threshold being lower than a maximum clamping force value exertable by the caliper; receiving (506) a reference force value (FR); identifying (508) a caliper stiffness model defined by a theoretical stiffness curve relating the clamping force applied by the caliper to the position of the caliper actuator, using a caliper stiffness modeling module; estimating (510) an estimated clamping force value (FS) using the caliper stiffness model and information about the position of the caliper actuator with a force estimation module; generating (512), by a brake control module, an actuator control signal (SC) based on the estimated clamping force value (FS) and the reference force value (FR).

2. 2. The method of claim 1, wherein the reference force value (FR) is received by a vehicle control module (101) that generates the reference force value (FR) based on a braking request (RF).

3. the caliper sensor has a reading range from at least zero to the clamping force threshold; 3. The method of claim 1, wherein if the reference force value (FR) is lower than the clamping force threshold, the method comprises generating (512') by a brake control module an actuator control signal (SC) based on the clamping force detected by the caliper sensor.

4. the caliper sensor has a reading range from zero to at least the clamping force threshold; The method of claim 1 , wherein the determining step (508) is performed based on information of the clamping force detected by the caliper sensor as a function of status information of the caliper actuator.

5. The method of claim 1 , wherein the identifying step (508) comprises generating a theoretical stiffness curve of parabolic, cubic, or exponential type over the entire operating range of the caliper.

6. 2. The method of claim 1, wherein the identifying step (508) comprises generating a theoretical stiffness curve having a first curve section of parabolic, cubic, or exponential type in a force range up to the clamping force threshold, and a second linear section above the clamping force threshold obtained by linear extrapolation starting from a slope of a terminal portion of the first curve section.

7. The method according to any one of claims 5-6, wherein the determining step (508) is performed in real time with each new cycle of obtaining information provided by the caliper sensor.

8. The method of claim 1 , wherein the determining step (508) is performed at the end of a braking event using a plurality of pieces of information provided by the caliper sensors during the braking event.

9. The method of claim 4 , wherein the determining step (508) is performed during a braking event each time a predetermined force sub-threshold is exceeded within a force range up to the clamping force threshold.

10. The method of claim 4, wherein the determining step (508) includes assigning, by a force estimation module, a greater weight to the most recent clamping force information provided by the caliper sensor.

11. 3. The method of claim 1, wherein the caliper sensor is a binary sensor adapted to provide clamping force presence / absence information when the clamping force reaches the clamping force threshold.

12. the determining step (508) further comprises estimating caliper hysteresis effects; The method of claim 1 , wherein the estimating step comprises a predetermined amount of change in a measured stiffness curve representative of an increasing trend in force during a braking event.

13. the determining step (508) further comprises estimating caliper hysteresis effects; The method of claim 1 , wherein the estimating step is based on detecting a clamping force of the caliper by the caliper sensor during a step of releasing a braking event.

14. A control system (100) for a vehicle braking system, comprising: a force sensor operatively associated with a brake caliper at a corner of the vehicle; an actuator sensor operatively associated with the electromechanical or electrohydraulic brake caliper actuator; a caliper stiffness modeling module; a force estimation module; A brake control module is provided.

10. A brake control system, wherein the control system is configured to perform the steps of the control method of claim 1.

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